This invention relates to an electric circuit board with a current sensor for one of the current traces thereon and a method for assembling the board and sensor.
It has been long known that an electric current through a current conducting element can be sensed by sensing a magnetic field surrounding the current conducting element. This magnetic field can be concentrated by a flux member surrounding the current conducting element which creates a magnetic circuit and includes a magnetic sensor. The principle is used in prior art devices such as the Hall-effect current clamp shown in U.S. Pat. No. 4,704,575, issued to Arnoux et al on Nov. 3, 1987, in which members 5a and 5b comprise a magnetic circuit including Hall effect cell 8, which circuit will respond to current through a conductor 6 when the magnetic circuit surrounds the conductor. A similar arrangement is shown in the Gary U.S. Pat. No. 4,639,665, issued Jan. 27, 1987.
However, the particular apparatus shown in these prior art patents is not particularly suited to circuit board applications, due to its size and the fact that no method for attaching the apparatus conveniently and securely to the circuit board is shown. In particular, the flux member for such apparatus in the prior art is generally made from a crystalline ceramic ferrite, which has favorable eddy current and hysteresis properties but, due to its hard and brittle nature, is expansive to manufacture, inflexible, easily broken and difficult to mount on a circuit board.